Boot: Sync MCUBoot code base

The MCUBoot files were added from the original MCUBoot
repository with version 1.0.0 and since then the code bases
have diverged from each other significantly. This patch
performs a partial synchronization between the MCUBoot files
in TF-M and in the original repo.
The hash of source commit in the original MCUBoot repo:
178be54bd6e5f035cc60e98205535682acd26e64.

The flash interface has also been extended and this patch
includes the implementation of these new functions too.

Change-Id: I16897ba884b56f90c9d35f99b709de86704a11ad
Signed-off-by: David Vincze <david.vincze@arm.com>